https://medium.com/@copyconstruct/nonblocking-i-o-99948ad7c957
https://idndx.com/2014/09/02/the-implementation-of-epoll-2/
http://www.cnhalo.net/2016/06/13/linux-tcp-establish/
https://www.codeblogbt.com/archives/460207
https://medium.com/@copyconstruct/the-method-to-epolls-madness-d9d2d6378642
https://www.codeblogbt.com/archives/460207
https://idea.popcount.org/2017-02-20-epoll-is-fundamentally-broken-12/
https://idea.popcount.org/2017-03-20-epoll-is-fundamentally-broken-22/